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C. L. DUNHAM.

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Pateted May 20, 1919.

N" www To all whom t ali/concern:

Be it known that I, CHARLES L. DUNHAM, a citizen of the United States, residing at Pennsboro, in the county of Ritchie and State of West Virginia, have invented certain new and useful Improvements in Underreamers, of which the following is a specification.

This 'invention relates to an under-reamer for oil wells but'it is to be understood that the device is designed for any Ipurpose whereinV it is found applicable and the in-v vention has for its object to provide, in a manner as hereinafter set forth, an under-1 reamer which-fis simple in its construction and arrangement, vformed of `few parts, readily assembled, eiiiclent 1n its use and comparatively inexpensive.

' throughout the several views:

` `VVith the'foregoing and vother objects in view this invention `consists of the novel construction, combination and arrangement of parts, as hereinafter more speciiically described and illustrated in the accompanying diawinos wherein is shown an embodiment.-

of the invention, but itis to be understood that changes, variations land modifications cany be resortedv to which come within the scope'of the claim hereunto appended.

In` the drawings wherein like reference'` characters denote corresponding `parts Figure 1 isfanelevationfof an underreamer, partly broken away, in accordance. with this invention. l.

Fig. 2 is a vertical sectional view thereof extended into a casing.

-Fig. 3 is lan inverted plan.

Referring to the drawings in `detail 1 denotesa shank and 2 thebodyportion of thek reamer, the-latter is formedwith' ahori- Zontal opening 3, "which extends in the direction of the length thereof. The body por-4 tion 2 has a lengthwise slot 4, disposed cen'- trally thereof near; its lower end andy which.

communicates with the opening 3 centrally of the bottom wall thereof, and alsofop'ens in the furcation 5 of the' bifurcated lowe therethrough.

end 6, of the body portion 2.

The furcation 5, of the bifurcated lower end 6, of the body portion 2, in connection with the slot 4,.'provides transverse shoulders 7 8, and inclined bearingsurfaces 9, 10.'

l The upper wall of the opening 3, is roundi ed and secured thereagainst by the yhold-fast device 11, is a substantially yoke-shaped' Specification of I Lettersyatent. l

z PENNSBQRQ, WEST Vvil-Rein*IA- 12, normally having the ends 13,

disposed counterb'alanced cutters, and each of which comprises a segment-shaped head 16, permanently disposed below the lower end of the body portion 2, 'and formed with inclined tops 17, which normally abut against the bevel portion 18 formed on the lower end of the body portion 2.

The heads l16 are oppositelyy disposed and.

each of which has formed integral centrally of its top, a flat shank 19, having an enlarged lower portion eccentrically mounted on a pin 15. The shank 19,has a squared shoulder 20, and a rounded shoulder 21. The latter abuts against the shoulder 9, and

il rammed Mayamaw." Application filed vSeptember 1 2, 1918i. Serial No. 253,805.

the former engages the bearing surface 7.

The upper portion of each of the shanks 19, is taperedy as at 22, and inset with respect to i the enlarged lower portion of the shank 19. The tapered upper portions of the Shanks 19, `when the cutters are in normal position abut,

andthe upper ends of said tapered portions permanently extend into the spring 12, be-` tween the arms 13 thereof whereby said arms will bearagainst the tapered upper portions In Fig. 2 of the drawings, the l casing or 22, and in accordance withthe weight of the `pipe is indicated at 23, andthe diameter of the casing is such that it engages the heads i 16, and cutters shift them inwardly wherevby the upper Sends of the Shanks 19, are 'moved apart against the action of the spring 12. Y

Each of the heads 16, has its periphery throughout uponthe arc of a circle, from `the top `to the bottom of the head, as at 25, Lto prevent any possibility of binding between the periphery and the inner face or joints of the casing when'inserting the same cured therein and having the legs thereof 1 normally extending toward each other, said body portion having a bifurcated lower end land further having a lengthwise opening communicating with a horizontal opening springysaid Shanks provided with rounded and with thefurcaton of said end, the rwalls; and flat shoulders engaging the bearing sur- 10 of said lengthwise opening forming inclined face and shouldersof the body portion, and bearing surfaces and the top wall of Said furcutter `heads carried by the Shanks and ar- 5 cation provide fiat shoulders, Shanks eccenranged eXteriorly of the body portiom trcally pivoted in the bifurcated endv of said In testimony whereof I affix mysignature.

body portion and extending into the horizontal opening and between the legs of said CHARLES L. DUNHAM,

Copies of this patent may be obtained for ive een'cs` ea/oh, by mgdressinig the Comminioner of Patents, Washington, 13.6." i 4 i 

